Maybe in some cases when the games were hard coded at 30fps (like Horizon or Bloodborne) those long hours of tests would be justified (but we haven't seen any of those patches for those games yet). BTW one guy actually patched bloodborne to run at 60fps without the source code just half guessing / working on the binaries by comparing with DS3 binaries. True story.
I think there aren't 60fps patches because the devs don't care and there is clearly not a will from the current boss to patch those "they look ancient, why would anybody play this" old games.
So right in february 2021 (after 1 or 2 years-ish of hard work from them owning PS5 devkits) they finally patched God of War 2018 with a 4K + 60fps patch for PS5. Impressive work.
Wait it's a free update for 4K CBR running at 60fps on PS5? How generous of them to give us the 1.0 disc version already QA tested since years ago.
And what about The last guardian, same thing, the 1.0 is already QA tested for 60fps gameplay (and runs perfectly on PS5), where is the patch?